1. Field of the Invention
This invention relates to a vapor growing method of a gold (Au) thin film, particularly a gold thin film having a flat surface, on a substrate.
2. Description of the Related Art
A thin film of aluminum (Al), etc., has been used primarily as a material of a wiring layer of an LSI, and the like.
However, when the aluminum thin film is used as the material of a wiring layer, electromigration and corrosion are likely to occur, so that degradation of the characteristics of LSIs, etc., and the reduction of the service life of these devices occur.
To eliminate these problems, the use of gold, which is highly resistant to electromigration and corrosion and can ensure high reliability for an extended period of time even in a corrosive environment, as the wiring layer material has been considered.
To obtain a thin film single crystal it has been possible conventionally to grow the thin film using a molecular beam epitaxy method, a cluster ion beam method and a gas temperature control method. However, step coverage necessary for LSI wirings has been difficult to attain using the first two of these methods, and up until now a report has only been made on the Al growth using the gas temperature control method. Therefore, a gold wiring layer by CVD (Chemical Vapor Deposition), having excellent step coverage properties, is preferable, but it has not been possible to form a flat thin film except by thermal excitation CVD of Al.
When about 1 .mu.m-thick gold thin film is formed at a practical growing rate of 10 .mu.m/hr using the conventional CVD process, a needle-like crystal grows on the surface of the thin film. It has therefore been extremely difficult to obtain a gold thin film having a thickness sufficient to serve as a wiring layer and a flat surface at such a practical growing rate.